Why canít I use certain words like "drop" as part of my Security Question answers?
There are certain words used by hackers to try to gain access to systems and manipulate data; therefore, the following words are restricted: "select," "delete," "update," "insert," "drop" and "null".

Is there a way to find at least 2 of the words is the search text if 2 of more search words are entered?

Loop method (as Jacques posted): count the number of times you find a word, make sure it's at least 2.
Regex method: preg_match_all(), array_unique() on the [0] array of matched words, count() that it's at least 2.

Why canít I use certain words like "drop" as part of my Security Question answers?
There are certain words used by hackers to try to gain access to systems and manipulate data; therefore, the following words are restricted: "select," "delete," "update," "insert," "drop" and "null".

I am not using PHP (not that I have anything against it, I learnt the basics of it a few years back and found it interesting, but it turned out not to be the best tool for the type of work I am diong), but I would think that with the loop method proposed by Jacques, you'll have to use some PHP finction to make everything lowercase before you start to compare; with a regex method, the regex /i qualifier will probably suffice. (Sorry if my answer is too Perlish and not really PHPist, but the /i qualifier is very general, working with sed, grep, ed, vi, awk, Perl, etc. I don't know how the "i" qualifier is specified in the PHP or PCRE or whatever regex module you are using).